Full bore or Reduce bore 1

[jeanfrancois3869]

Hi,

What are the advantages or disadvantage of full bore or reduced valve? In my case, I want install Trunion DBB valves for the sectioning but I dont't know if I must choose a reduced or full bore valves.

Thank you to help me.

 

[Latexman]

Tell us your application details. We are not Nostradamus.

Good luck,
Latexman

 

[jeanfrancois3869]

The application is an integrated gas and iquid hydrocarbon system. In fact, I have 2 types of valve:
-1 DBB valve (Trunion mounted ball valve)for double insulation and sectioning (upstream and downstream)
-1 Globe Valve to regulate the flows

The pressure in the system comes from 60 to 100 bars.

 

[pennpiper]

jeanfrancois3869,
The terms "Full Bore" and "Reduced Bore" do not apply to the Globe Valve.

The terms "Full Bore" and "Reduced Bore" do apply to the Ball Valves.

You should use a "Full Bore" Ball Valve if (and only if) you are going to be running a "Pig" through these lines.

If you do not plan on running any "Pigs" then you should use the cheaper of the two (normally the Reduced Bore).

The minor effect of any flow restriction caused by the reduced bore (versus the full bore) will not be measurable in the overall system analysis.

 

[rneill]

You mention DBB valve but just a caution that this terminology is not always consistent and you might need to clarify what specifically you are looking for.

Most manufacturers (and Valve standards) refer to Double Block and Bleed as meaning the valve can block pressure from either upstream or downstream while bleeding the body cavity. The seats are direction and self relieving which means that if for some reason you were blocking upstream pressure and there was no pressure downstream. If the upstream seat failed, and the bleed was closed, the downstream seat would self relieve and the fluid would flow downstream.

Often people want to provide "Double Block and Bleed" to provide double redundancy to protect a downstream system from seeing pressure. Used in this context, they want the secondary block to act as a backup to the primary seat. This does not happen in a typical trunnion mounted DBB valve due to the self relieving.

Some valve manufacturers (Grove, Nuovo Pignone) provide trunnion mounted ball valves that do not have the self relieving feature and do provide redundant double block capability. However, these valves can be subject to failure if the bleed is blocked shut and the body cavity is full of liquid and the valve heats up since the fluid wants to expand and has nowhere to go.

Anyway, important to understand exactly what you want and to ensure that you get the correct type of DBB for your application. Some Occupational Health and Safety Regulations (in some jurisdictions) will specify the use of DBB in some circumstances and when they do, they would generally be referring to the valves that did not have self relieving seats.

The cost difference between regular port and full port ball valves is not what it used to be (typically less than 15%) so some people standardize on full port to reduce handling and inventory issues but as pennpiper mentions, full port is not typically required (may be required for pigging, on relief lines, adjacent to flow meters or check valves to minimize flow disturbances, pump suction lines, etc.)

 

[jeanfrancois3869]

Thank you to help me, all the informations are going to be usefull for my work.

 

[zdas04]

Penpiper,
Have you checked with a valve manufacturer lately? Last time I checked full bore valves between 6-inch and 24 inch were all less expensive than reduced bore valves--they told me that the demand for reduced bore valve had dropped off so much that they don't keep the parts like they used to. With the pipeline inspection laws that were put in place after the EPNG pipeline roasted that family in southern New Mexico, many "non piggable" lines had to be retrofit. People are starting to understand that using reduced port valves is a false "economy" (especially when they can actually be higher priced). My recommendation to folks is exactly 180 degrees from yours, I say always get full port unless there is a compelling reason not to.

rneil,
Really good point about jurisdiction on DBB. OSHA is silent on what would qualify, but at least one of the Scandinavian countries specifically excludes Trunnion Ball valves from qualifying as DBB. Where the law is silent, company policies kick in. I have one client that says Trunnion Ball valves (without mentioning the self-relieving point you raise) are OK, another says they are not.

David

 

[pennpiper]

zdas04,
Thanks for the information on the current pricing outlook for "Ball Valves". My information does have a bit of rust on it.

 

[eadwine]

Pig usage isn't always the case for specing full bore valves. There are times in polymer applications where full bore valves allows the use of smaller pumps (less cost) due to their decreased pressure drop as opposed to reduced port valves which increase pressure drop requiring larger pumps.

There is also the issue of incrreased turbulence with reduced ports which can break up the polymer matrix.

 

[rmw]

What you would have on a globe valve is a reduced trim size instead of a reduced bore.

rmw

 

[jeanfrancois3869]

To answer to rneill, I want to be able to isolate a line equipped in upstream and downtream with a simple DBB valve to change components (filter,flow conditionner. The DBB Valve is composed with a simple ball with a drain plug to empty the body cavity. on the both side (in upstream and downstream) of the body there are springs which maintain the proof forcing the seat rings against the ball.
For gas application, the line are also equipped to vent to bleed the line.

I know a german manufacturer, the valves whose I speak are like HKSF-W see to:

 

[rneill]

jeanfrancois3869,

I took a look at the valve (HKSF-W) and noted a few things ...

- It is a welded body metal seated ball valve. These would normally be reserved for very critical or high temperature services. We would not typically use these sorts of valves for routine hydrocarbon (oil and gas) services at near ambient temperatures (less than perhaps a max of 150 C).

- This valve is available as either single piston design or double piston design. The single piston version has self relieving seats and is not what I would call true "DB&B". The double piston version does not have self relieving seats and is what I would call true "DB&B". My definition of true DB&B being that the downstream seat can act as a redundant backup in the event up upstream seat failure.

It sounds like you want DB&B for process isolation purposes so you would most likely want the double piston version. If you order the double piston version for a liquid line, you would want to equip it with a thermal relief (and manual bypass) on the body cavity to prevent the problems I mentioned earlier.